ArcGIS Online API Build

I normally develop apps around Portal for ArcGIS. The reason is that Portal gives me an API that I can trust since I know that the release version won't change unless I want it so. Unfortunately, ArcGIS Online is not ideal for custom development as the interfaces may change from release build to release build.

It would be great if ArcGIS Online had available all the previous API versions. Clients would invoke the AGOL REST API passing optionally the version of the API they are trying to execute. If no version is specified then the last one (default) is used.

Apps like Collector for ArcGIS could have an option in the Settings menu where you specify the API version you want to use.

This would expand the number of use cases where ArcGIS Online is applicable. Developers would be able of developing customised apps referencing a particular API version from ArcGIS Online knowing that even if the AGOL REST API updated their app is safe and that its functions will still be supported if AGOL is upgraded.